Burster RESISTOMAT 2408, Manual, Page: 43 / 90

Model 2408
RESISTOMAT
®
Page 43
Table 2-1: Range Current
Range Maximum Current
1 1 mA
2 100 µA
3 10 µA
4 1 µA
5 100 nA
6 10 nA
7 1 nA
Example:
When measuring an unknown of 200 M
Ω
at 100 V, Ohm’s Law tells us that the device under
test would draw 0.5 µA (I = 100 V/200 M
Ω
). Based on the above, one would expect the 2408
instrument to auto-range from the 1 mA to 1 µA range (50% of maximum current), or that
the user should select the 1µA range based on prior knowledge of the expected results.
NOTE
When measuring in the current mode, in order to calculate the unknown resistance, the
input resistance of the instrument (5 k
Ω
) must be taken into consideration.
For further discussion of this refer to Display Type in Paragraph 2.6.3.1
The measurement range capability is represented graphically in Figure 2-14. By locating
the charge voltage on the vertical axis and the measured resistance – or expected mea -
sured resistance – on the horizontal axis, one can determine the optimum range. When
Auto-Range is selected, the range switching is done automatically and the specified instru
-
ment accuracy always applies. If a range other than Auto is selected, and the resistance
value for the given voltage falls outside the range band shown, the measurement accuracy
specified does not necessarily apply.